Recent advances in wireless communications and electronics have enabled the development of low-cost sensor nodes. Each sensor node can sense specific events in its vicinity, such as motion, noise, vibration or environmental conditions, and communicate with adjacent nodes. Thus, for event sensing applications, a large number of sensor nodes are deployed in a target field and they collaborate to form an ad-hoc network, referred to as a wireless sensor network. When a sensor detects an event, the sensor reports the event to a data collection center, referred to as a base station (BS), that may be several hops away.
WSNs provide significant improvements over traditional sensing means, since they collect monitoring information from numerous locations in the target field. Therefore, they have the potential to take on a major role in many civil and military applications, such as intrusion detection and environmental monitoring. Many of these applications are mission critical and require reliable detection of hazardous events. For such applications, a WSN typically must guarantee a reliable detection of the specified events. Therefore, the coverage of the target field is often considered as a measure of the Quality of Service (QoS) guaranteed by the WSN.